Pseudocode IF ... THEN ... ELSE ... ENDIF

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Quick Questions

Shade in the A or B circle for each question.

1. Which IF statement is written correctly in Cambridge pseudocode?

A IF score >= 50 THEN OUTPUT "Pass" ENDIF

B IF score >= 50 THEN OUTPUT "Pass" END

2. Where should ENDIF be placed?

A Indented in line with the statements after THEN

B At the same indent as the IF it closes

3. What happens when the condition in an IF ... THEN ... ELSE ... ENDIF is false?

A The indented lines after THEN are run

B The indented lines after ELSE are run

4. What happens when an IF with no ELSE has a false condition?

A The program skips to the line after ENDIF

B The program stops with an error

5. Which condition correctly checks that age is not equal to 18?

A IF age <> 18 THEN

B IF age =! 18 THEN

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1IF score >= 50 THEN		AIF temp > 30 THEN OUTPUT "Hot" ELSE OUTPUT "Not hot" ENDIF
2ELSE		BStarts a selection: the indented lines below run only when score is 50 or more
3A one-way IF with no ELSE: nothing happens if the condition is false, and ENDIF closes it at the same indent as IF		CThe ENDIF is missing, so the IF construct is never closed. Add ENDIF at the same indent as IF after the ELSE lines.
4A two-way IF with ELSE: one set of lines runs if the condition is true, a different set runs if it is false		DIF age < 18 THEN OUTPUT "Under 18" ENDIF
5IF score >= 50 THEN OUTPUT "Pass" ELSE OUTPUT "Fail"		EENDIF is indented as if it were inside the IF. It must line up with IF at the same indent.
6IF mark = 100 THEN OUTPUT "Full marks" ENDIF		FIntroduces the lines that run when the IF condition is false

Definitions

IF THEN ELSE ENDIF

Fill in the Blanks

Complete each line of code by filling in the missing parts.

IF Age >= 18 ____ OUTPUT "Adult" ENDIF

IF Score __ 50 THEN OUTPUT "Pass" ENDIF

IF Temp < 10 THEN OUTPUT "Cold" _____

____ OUTPUT "Fail" ENDIF

IF Pin __ 1234 THEN OUTPUT "Wrong PIN" ENDIF

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A IF score >= 50

B OUTPUT "Pass"

C ELSE

D OUTPUT "Fail"

E ENDIF

Question 2

A INPUT age

B IF age > 18 THEN

C OUTPUT "Minor"

D ELSE

E OUTPUT "Adult"

F ENDIF

Question 3

A INPUT guess

B IF guess = 7 THEN

C OUTPUT Correct

D ELSE

E OUTPUT "Wrong"

F ENDIF

Question 4

A INPUT mark

B IF mark => 40 THEN

C OUTPUT "Pass"

D ENDIF

Question 5

A IF lives ← 0 THEN

B OUTPUT "Game over"

C ENDIF

Answer Key

Pseudocode IF ... THEN ... ELSE ... ENDIF

Section A: Quick Questions

A — IF score >= 50 THEN OUTPUT "Pass" ENDIF

B — At the same indent as the IF it closes

B — The indented lines after ELSE are run

A — The program skips to the line after ENDIF

A — IF age <> 18 THEN

Section B: Match the Pairs

IF score >= 50 THEN → Starts a selection: the indented lines below run only when score is 50 or more

ELSE → Introduces the lines that run when the IF condition is false

A one-way IF with no ELSE: nothing happens if the condition is false, and ENDIF closes it at the same indent as IF → IF age < 18 THEN OUTPUT "Under 18" ENDIF

A two-way IF with ELSE: one set of lines runs if the condition is true, a different set runs if it is false → IF temp > 30 THEN OUTPUT "Hot" ELSE OUTPUT "Not hot" ENDIF

IF score >= 50 THEN OUTPUT "Pass" ELSE OUTPUT "Fail" → The ENDIF is missing, so the IF construct is never closed. Add ENDIF at the same indent as IF after the ELSE lines.

IF mark = 100 THEN OUTPUT "Full marks" ENDIF → ENDIF is indented as if it were inside the IF. It must line up with IF at the same indent.

Section C: Definitions

IF THEN ELSE ENDIF — Runs the indented lines after THEN if the condition is true, otherwise runs the ELSE lines. ENDIF closes the construct and sits at the same indent as IF. ELSE is optional.

Section D: Fill in the Blanks

IF Age >= 18 THEN
  OUTPUT "Adult"
ENDIF

IF Score >= 50 THEN
  OUTPUT "Pass"
ENDIF

IF Temp < 10 THEN
  OUTPUT "Cold"
ENDIF

ELSE
  OUTPUT "Fail"
ENDIF

IF Pin <> 1234 THEN
  OUTPUT "Wrong PIN"
ENDIF

Section E: Spot the Error

A — The IF line is missing THEN. The condition must be followed by THEN, so it should be IF score >= 50 THEN.

B — The comparison operator is the wrong way round. Minor should be shown when age is less than 18, so the line should be IF age < 18 THEN.

C — The text to display is missing its quote marks. Without them Correct looks like a variable. It should be OUTPUT "Correct".

B — The comparison operator is written the wrong way round. 'Greater than or equal to' is >=, not =>.

A — ← is for assignment, not for comparing. A condition that tests equality uses =, so it should be IF lives = 0 THEN.